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Identification and Temperature Regulation ofLegionella pneumophila Genes Involved in Type IV Pilus Biogenesis and Type II Protein Secretion

机译:涉及IV型毛囊生物发生和II型蛋白分泌的嗜肺军团菌基因的鉴定和温度调控

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Previously, we had isolated by transposon mutagenesis aLegionella pneumophila mutant that appeared defective for intracellular iron acquisition. While sequencing in the proximity of the mini-Tn10 insertion, we found a locus that had a predicted protein product with strong similarity to PilB fromPseudomonas aeruginosa. PilB is a component of the type II secretory pathway, which is required for the assembly of type IV pili. Consequently, the locus was cloned and sequenced. Within this 4-kb region were three genes that appeared to be organized in an operon and encoded homologs of P. aeruginosa PilB, PilC, and PilD, proteins essential for pilus production and type II protein secretion. Northern blot analysis identified a transcript large enough to include all three genes and showed a substantial increase in expression of this operon when L. pneumophila was grown at 30°C as opposed to 37°C. The latter observation was then correlated with an increase in piliation when bacteria were grown at the lower temperature. Southern hybridization analysis indicated that the pilBlocus was conserved within L. pneumophila serogroups and other Legionella species. These data represent the first isolation of type II secretory genes from an intracellular parasite and indicate that the legionellae express temperature-regulated type IV pili.
机译:以前,我们通过转座子诱变分离了一个肺炎军团菌突变体,该突变体似乎对细胞内铁的获取有缺陷。在mini-Tn 10 插入序列附近进行测序时,我们发现了一个位置,该位置的预测蛋白产物与铜绿假单胞菌(Pseudomonas aeruginosa)的PilB具有高度相似性。 PilB是II型分泌途径的组成部分,这是IV型菌毛组装所必需的。因此,基因座被克隆并测序。在这个4kb区域内,有3个基因似乎在操纵子中组织并编码了 P的同源物。铜绿菌PilB,PilC和PilD,它们是菌毛产生和II型蛋白质分泌必不可少的蛋白质。 Northern印迹分析鉴定出足以包括所有三个基因的转录本,并显示当 L时该操纵子的表达显着增加。嗜肺菌在30°C(而不是37°C)下生长。当细菌在较低温度下生长时,后者的观察结果与毛发增加相关。 Southern杂交分析表明, pilB 基因座在 L内是保守的。肺炎血清群和其他物种。这些数据代表首次从细胞内寄生虫分离II型分泌基因,并表明军团菌表达了温度调节的IV型菌毛。

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